1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device that secures sufficient writing time to store video signals at a high frame frequency and driving method thereof.
2. Discussion of the Conventional Art
As the information age advances, the requirements of display devices are increasing. To satisfy these requirements, some of the various flat display devices such as a liquid crystal display device (LCD), a Plasma Display Panel (PDP), and a Electro Luminescent Display (ELD) have been developed, and some are already used as display devices in many types of equipment.
Among the above-mentioned devices, the liquid crystal display device is currently the most widely used to substitute for cathode ray tube displays for use in mobile image display devices with the advantages of high video quality, light weight, thin form, low power consumption, and liquid display devices have been developed and not just for mobile devices such as monitors of notebook computers, but also for television monitors.
The liquid display device displays images using the optical anisotropy and the polarizing quality of the liquid crystal. The liquid molecules included in the liquid crystal may be arranged in a predetermined or a regular direction. Also, the arrangement direction of the molecules of the liquid may be controlled by an electric field applied to the liquid crystal. Therefore, if the arrangement direction of the molecules of the liquid is controlled, the arrangement direction of the liquid crystal molecules is changed, and image information is presented by changing the polarized state of the light in the arrangement direction of the molecules of the liquid due to the optical anisotropy.
The liquid crystal display device as describe above has a liquid crystal panel that displays an image, and a drive unit operating the liquid panel. The liquid crystal panel has a liquid crystal layer formed between the two substrates. One of the substrates has pixel electrodes in each of the pixel regions divided by a plurality of gate lines and a plurality of data lines crossing each other. A liquid crystal cell includes a pixel electrode, a common electrode formed on one of the two substrates, and a portion of the liquid crystal layer. Further, each crossing of the gate lines and the data lines includes a thin film transistor. The thin transistor switches the supplied data signals to the corresponding pixel electrode from the corresponding data lines in response to the gate signals (or scan signals) on the corresponding gate lines. The liquid crystal cells in the liquid crystal panel are sequentially accessed line by line with the data signals supplied to the plurality of data lines whenever the plurality of gate lines are enabled sequentially by the gate signals. Accordingly, images corresponded to the video data are displayed by controlling the arrangement direction of the liquid crystal molecules.
The drive unit includes: a gate driver driving the gate lines on the liquid crystal panel; a data driver driving the data lines on the liquid crystal panel; and a timing controller controlling the driving timing of the gate driver and the data driver. Furthermore, the liquid crystal display device includes a back light unit irradiating light to the liquid crystal panel.
The liquid crystal display device described as above drives the liquid crystal panel with a frame frequency of 60 Hz. That is, the liquid crystal display device displays 60 pages of pictures per second. When the video pictures are displayed on a liquid crystal panel with a frame frequency of 60 Hz, motion blurring is generated. Accordingly, it was difficult to display motion pictures with good quality through the liquid crystal display device driving the liquid crystal panel at a frame frequency of 60 Hz.
To overcome the above-mentioned disadvantage, a liquid crystal display device driving the liquid crystal panel at a frame frequency of 120 Hz is being proposed. The liquid crystal display device with the frame frequency of 120 Hz exchanges images at a speed twice as fast as the liquid crystal display device with a frame frequency of 60 Hz.
In another solution that has been proposed, a pseudo-impulsive liquid crystal display device drives the liquid crystal cells in the liquid crystal panel in a form of impulse. The pseudo-impulsive liquid crystal display device writes data signals and black signals alternatively on the liquid crystal cell of the liquid crystal panel. The liquid crystal panel is also driven at 120 Hz in the pseudo-impulsive liquid crystal display device. On each of the liquid crystal cells on the liquid crystal panel, video signals and black signals are displayed 60 times alternatively. That is, the liquid crystal panel is also driven at 120 Hz in the pseudo-impulsive system.
As described above, when the liquid crystal panel is driven at a frame frequency of 120 Hz, the enabling period of each of the gate lines on the liquid crystal panel is reduced in half as compared with the liquid crystal display device with a frame frequency of 60 Hz. Accordingly, sufficient time for the data signals to be written on the cells of the liquid crystal as passing through the thin film transistor is difficult to achieve. Further, the quality of the pictures displayed using the liquid crystal display device of frame frequency of 120 Hz becomes lower.